Integrated circuits are commonly mounted in chip carriers which are bodies of insulating material having side surfaces to which conductors from the integrated circuit extend. Terminal pads are provided on the side surfaces of the chip carrier body and contact is made with these pads to connect the integrated circuit to conductors on a substrate such as a ceramic substrate or a circuit board. Contact is usually established with the terminal pads on the chip carrier by means of a chip carrier socket which comprises a socket body having a recess which receives the chip carrier and contact terminals in surrounding relationship to the recess so that when the chip carrier is placed in the recess, the contact terminals contact the terminal pads of the chip carrier.
A chip carrier socket is thus a specialized type of multicontact electrical connector. However, the design and performance requirements of a chip carrier socket exceed the requirements of previously known connectors used for connecting terminals to circuit boards or the like. Chip carriers are quite small and the terminal pads on chip carrier are commonly space apart by about 0.025 inches (0.6 mm), although chip carriers are now being proposed having a center-to-center spacing of the terminal pads of only 0.01 inches (0.25 mm). The close spacing of the terminal pads on the chip carrier requires as a general rule that the contact terminals be of the complanate type, that is that they be flat terminals having a thickness equal to the thickness of the stock metal from which they were stamped. If the chip carrier socket is intended for a chip carrier having terminal pads spaced at 0.050 l inch intervals (1.3 mm), the contact terminals are commonly produced from metal stock having a thickness of 0.02 inches but it is often necessary to produce contact terminals having a thickness of 0.01 inches or less.
Chip carrier sockets commonly have a height of about 0.4 inches (10 mm) and the terminals may have a height of no more than about 0.3 inches (7 mm).
Notwithstanding the relatively small size of the chip carrier socket and the contact terminals in the socket, is is necessary that each terminal be capable of exerting of contact force on a terminal pad in a chip carrier in the range of about 200 to 400 l grams in order to establish good electrical contact between the contact terminal and the terminal pad on the chip carrier, particularly if the terminal pad is tin plated rather than gold plated. Finally, chip carriers and chip carrier sockets are subject to the dimensional variations of all mass produced parts which result from manufacturing tolerances and the design and performance requirements discussed briefly above must be satisfied even in "worst case" conditions. For example, the minimum 200 gram contact force required for each contact must be met even if the particular terminal pad that a contact terminal engages is at the lower end of the tolerance range and the contact terminal similarly is at the lower of the tolerance range for the parts.
It can be appreciated from the foregoing remarks that many of the types of contact terminals used in prior art connectors are not suitable for use in chip carrier sockets and would not satisfy the requirements of a chip carrier socket terminal. The present invention is specifically directed to the achievement of an improved chip carrier socket and contact terminal which is capable of satisfying the requirement discussed above.